Multiple sclerosis (MS) is a neurological illness of unknown etiology associated with attacks of focal or multifocal neurological dysfunction arising from lesions within the central nervous system (CNS). In America and Northern Europe, MS is the most common neurological disease, with prevalence rates estimated between 50-100 per 100,000 population. The onset of disease is most common in early adulthood. Recurrent attacks can occur over many years, with approximately 30 percent of the patients progressing to a severe form of the disease which can be fatal.
MS is pleomorphic in its presentation. The clinical manifestations are determined in part by the location of the foci of demyelination within the CNS. Classical features of the disease include impaired vision, nystagmus, dysarthria, ataxia and intention tremor, and weakness/paralysis of one or more limbs.
The most common form of the disease is episodic. Symptoms develop with subsequent recovery, then another attack occurs. In approximately 50 percent of all patients with MS, attacks become more frequent, usually with a worsening of symptomatology. In 30 percent of all patients, the disease develops into what is referred to as "progressive/relapsing," the most severe form of the disease. In this state remissions are rare and patients frequently become wheelchair bound.
The characterization of MS disease activity (including diagnosis, determination of disease state, monitoring of disease progression, prediction of disease attacks, and the like), remains problematic. To aid the clinician, the only laboratory test available is testing the cerebrospinal fluid for oligoclonal bands, present in approximately 90 percent of all patients. Examination of the brain for demyelinating plaques, using magnetic resonance imaging (MRI) is useful but expensive, and is not warranted except in a small group of patients in which all other clinical and laboratory tests are negative. Furthermore, there is no diagnostic laboratory test to determine if a patient is having an "attack," to monitor the progress of the "attack," to determine if the patient is progressing to a more active form of the disease (i.e., progressive/relapsing). Finally, there is no laboratory test available as a prognostic indicator and/or capable of monitoring the course of therapy. One commentator has summarized the situation as follows: "The need for reliable markers of disease activity in multiple sclerosis (MS) to better guide basic research, diagnosis, treatment, and monitoring therapy is well-recognized." Laman et al., Mult. Scler. (June 1998) 4:266-269.
As such, there is a need in the field to develop additional means for characterizing MS disease activity in a subject.